Android Drag and Drop Item in RecycleView.

1.Create an android application project in Studio

Create an android application project in eclipse. To drag and drop list items in list view, we need a custom list view. So first create a class for custom list view and extend it to ListView super class.

2.OnItemLongClickListener

Set OnItemLongClick listener in adapter view and create a hover cell for the selected item.

holder.rowView.setOnLongClickListener(View.OnLongClickListener {    
mStartDragListener.requestDrag(holder)
    true})

3. activity_main.xml file

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
        xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:tools="http://schemas.android.com/tools"
        xmlns:app="http://schemas.android.com/apk/res-auto"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        tools:context="android.com.androiditemdraganddrop.MainActivity">

    <androidx.recyclerview.widget.RecyclerView
            android:id="@+id/contactsRecycleView"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            app:layout_constraintTop_toTopOf="parent"
            app:layout_constraintStart_toStartOf="parent">
    </androidx.recyclerview.widget.RecyclerView>

</androidx.constraintlayout.widget.ConstraintLayout>

4. StartDragListener.kt  Interface

package android.com.androiditemdraganddrop

import androidx.recyclerview.widget.RecyclerView

interface StartDragListener {
    fun requestDrag(viewHolder: RecyclerView.ViewHolder)
}

5. MainNavigator.kt Interface

package android.com.androiditemdraganddrop

interface MainNavigator {

    fun onRecentActivityClick(accountName: String)
}

6. ItemMoveCallback.kt

package android.com.androiditemdraganddrop

interface MainNavigator {

    fun onRecentActivityClick(accountName: String)
}

Here is main adapter this adapter is use-full  to drag Item from one position to another position

7. MainAdapter.xml file

package android.com.androiditemdraganddrop

import android.content.Context
import android.graphics.Color
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.recyclerview.widget.RecyclerView
import kotlinx.android.synthetic.main.item_favorites.view.*
import java.util.*
import kotlin.collections.ArrayList
import kotlin.com.androiditemdraganddrop.R

class MainAdapter(
    private val context: Context,
    private val favoritesList: ArrayList<String>,
    private val mStartDragListener: StartDragListener
) :
    RecyclerView.Adapter<MainAdapter.MyViewHolder>(),
    ItemMoveCallback.ItemTouchHelperContract {

    lateinit var mListener: MainNavigator

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): MyViewHolder {
        return MyViewHolder(
            LayoutInflater.from(context).inflate(
                R.layout.item_favorites,
                parent,
                false
            )
        )
    }

    override fun getItemCount(): Int {
        return favoritesList.size
    }

    override fun onBindViewHolder(holder: MyViewHolder, position: Int) {
        holder.accountName?.text = favoritesList.get(position)

        holder.rowView.setOnLongClickListener(View.OnLongClickListener {
            mStartDragListener.requestDrag(holder)
            true
        })

        holder.itemView.setOnClickListener {
            mListener.onRecentActivityClick(favoritesList[position])
        }
    }

    class MyViewHolder(internal var rowView: View) : RecyclerView.ViewHolder(rowView) {
        val accountName = rowView.account_name
        val imgProfilePic = rowView.img_profilePic
    }

    override fun onRowMoved(fromPosition: Int, toPosition: Int) {
        if (fromPosition < toPosition) {
            for (i in fromPosition until toPosition) {
                Collections.swap(favoritesList, i, i + 1)
            }
        } else {
            for (i in fromPosition downTo toPosition + 1) {
                Collections.swap(favoritesList, i, i - 1)
            }
        }
        notifyItemMoved(fromPosition, toPosition)
    }

    override fun onRowSelected(myViewHolder: MyViewHolder) {
        myViewHolder.rowView.setBackgroundColor(Color.WHITE)
    }

    override fun onRowClear(myViewHolder: MyViewHolder) {
        myViewHolder.rowView.setBackgroundColor(Color.WHITE)
    }
}

Here is the  screen shorts.

Finally MainActivity.kt file to send data to adapter 

8.MainActivity.kt file

package android.com.androiditemdraganddrop

import android.os.Bundle
import android.widget.Toast
import androidx.appcompat.app.AppCompatActivity
import androidx.recyclerview.widget.ItemTouchHelper
import androidx.recyclerview.widget.LinearLayoutManager
import androidx.recyclerview.widget.RecyclerView
import kotlinx.android.synthetic.main.activity_main.*
import kotlin.com.androiditemdraganddrop.R

class MainActivity : AppCompatActivity(), StartDragListener, MainNavigator {

    private var mFavoritesAdapter: MainAdapter? = null
    private val mFavoriteList: ArrayList<String> = ArrayList()
    internal var touchHelper: ItemTouchHelper? = null

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        mFavoriteList.add("Account 1")
        mFavoriteList.add("Account 2")
        mFavoriteList.add("Account 3")
        mFavoriteList.add("Account 4")
        mFavoriteList.add("Account 5")
        mFavoriteList.add("Account 6")
        mFavoriteList.add("Account 7")
        mFavoriteList.add("Account 8")
        mFavoriteList.add("Account 9")
        mFavoriteList.add("Account 10")

        //Favorites list
        val layoutManager = LinearLayoutManager(this)
        contactsRecycleView!!.layoutManager = (layoutManager)
        mFavoritesAdapter = MainAdapter(this, mFavoriteList, this)

        val callback = ItemMoveCallback(mFavoritesAdapter!!)
        touchHelper = ItemTouchHelper(callback)
        touchHelper!!.attachToRecyclerView(contactsRecycleView)

        contactsRecycleView!!.adapter = mFavoritesAdapter
        mFavoritesAdapter!!.mListener = this
    }

    /*
    * This method used for requesting drag items.
    * */
    override fun requestDrag(viewHolder: RecyclerView.ViewHolder) {
        touchHelper!!.startDrag(viewHolder)
    }

    /*
    * This method used for fetching item details.
    * */
    override fun onRecentActivityClick(accountName: String) {
        Toast.makeText(this, accountName, Toast.LENGTH_LONG).show()

    }
}